Internet Engineering Task Force Request For Comments (RFC) 2475 sets out an architecture for differentiated services in the IP layer of a communications network. Also, RFC 2597 sets out an assured forwarding schema using differentiated services in the IP layer of a network. However, the proposals to date have relied on so-called “per hop” behaviour (PHB). This means that each router in the core network is required to operate according to the differentiated services protocols and in particular, is required to be able queue and/or drop packets in order to limit bandwidth travelling around the network to provide the differentiated services. In the case of core networks using photonic switches, this is presently not feasible since queuing and packet dropping of this type presently requires an optical-electrical-optical conversion which is prohibitively expensive. In order to implement the differential services, assured forwarding proposals in an optical (or photonic) network in which switching and routing within the core network is carried out purely in the optical domain, it is necessary to overcome the need for intelligent switches which can drop and/or queue packets.